1. Field of the Invention
The present invention concerns a system for determining comparative transport costs of long distance traffic to a long distance carrier having a point-of-presence in a local access and transport area by the addition of more point-of-presence, ant for determining the least cost routing of the long distance traffic through existing or candidate points-of-presence.
2. Description of the Prior Art
Local exchange carriers provide local telephone service within a geographical area which typically includes a so-called Local Access Transport Area (LATA). Long distance telephone service between LATA's is provided by long distance telephone companies also known as interexchange carriers. In order to provide long distance service, an interexchange carrier must have a so-called point-of-presence (POP) within each LATA in order to receive long distance traffic originating within the LATA from the local exchange carrier, and to transfer long distance traffic terminating within the LATA to the local exchange carrier.
A typical LATA includes a number of so-called end offices or local telephone exchanges to which individual telephones are directly connected. Telephone traffic between end offices is usually routed by way of a tandem switch which avoids the need for each end office to be directly connected to every other end office within the LATA. Instead, the tandem switch routes the telephone traffic, either originating or terminating, between end offices, between an end office and another tandem, or between an end office and the POP of an interexchange carrier.
In order to place a POP in a LATA, an interexchange carrier connects to an end office of the carrier's choice within the LATA. In this regard, the end office serves merely as a service wire center for the physical connections for placing the POP in circuit communication with the tandem switch by which long distance traffic is routed to and from the carrier's POP. A long distance call terminating within the LATA is transferred from the interexchange carrier's network to the tandem of the local telephone company by way of the carrier's POP. The tandem then routes the call to the end office to which the called customer is connected. Similarly, a customer's long distance call is routed from the customer's end office to the tandem switch which then transfers the call to the POP belonging to the interexchange carrier which the customer has designated for providing long distance service.
In return for providing these switching services, the local exchange carrier charges transport fees which are known as transport costs to the interexchange carrier. These transport costs are often in the form of a per minute charge based on the chargable distance or mileage between the customer's end office and the end office to which the carrier's POP is connected, for example. Thus, the farther the customer's end office is from the end office to which carrier's POP is connected, the higher the transport costs on a per minute basis.
The transport tariffs of the local exchange carriers vary considerably. For example, some tariffs are based on a straight mileage distance between end offices and some are on the basis of a banded mileage scheme.
So called meet-point tariffs are also involved if more than one local telephone company is operating within a given LATA. For example, the interexchange carrier may have its POP connected to one local telephone company and the customer may be served by the other. In this situation, the call is transferred from one local telephone company to the other and the applicable tariffs for each local telephone company must be taken into account to the "meet-point."
Determining transport costs is also complicated by the fact that some end offices are directly trunked to the carriers's POP thereby bypassing the tandem switch. Additionally a different tariff may apply for intrastate traffic between LATA's.
It maybe advantageous for a interexchange carrier to provide additional POP's within a LATA in order to minimize chargable distances and thereby minimize transport charges. In a densely populated LATA, however, literally hundreds of end offices may be present and determining the most economical location for one or more additional POP's can be difficult. In the prior art, this has been done be determining the weighted average transport cost based on actual mileage between end offices taking into account the volume of long distance traffic. This method may not be optimal, however, because of the complicated tariff structure. For example, the most economical transport cost may not necessarily result from the shortest mileage distance because of banded mileage charges and meet-point tariffs.
Furthermore, a method based strictly on distance between end offices does not necessarily provide the most economical routing when more than one POP is already present within the LATA. For example, if more than one POP is present in a LATA, the interexchange carrier can route traffic terminating within the LATA through the POP of choice. For calls originating within the LATA, however, a tandem through which the calls passes may be programmed to route all originating calls to only one POP. Hence, the most economical routing for originating traffic may be different than that for traffic terminating within the LATA.